The present invention relates to a clinch nut assembly and a method of producing a clinch nut, and more particularly to a clinch nut assembly, in which a clinch nut is previously fixed to a sheet metal, and a method of producing such a clinch nut.
As a nut previously fixed to a sheet metal, Japanese Laid-open Patent Publication No.sho.60-252814 discloses a clinch nut. As shown in FIG. 16, the clinch nut 51 comprises, on a bottom end surface facing to a sheet metal, an internal cylindrical portion 52 with a screw hole 53 for punching the sheet metal in order to provide a bolt insertion hole in the sheet metal and an external cylindrical portion 54. An annular groove 56 is formed coaxially with the screw hole 53 and between the internal cylindrical portion 52 and the external cylindrical portion 54. The external cylindrical portion 54 is shorter than the internal cylindrical 20 portion 52, and the inner peripheral surface 55 of the external cylindrical portion 54 is provided with an engaging part, which is of a reverse tapered shape extending from the bottom end surface, for interlocking with the periphery of the bolt insertion hole of the sheet metal.
As a nut having a similar construction to the aforementioned clinch nut 51, Japanese Laid-open Patent Publication No. Hei 11-193808 discloses a pierce nut. As shown in FIG. 17, the pierce nut 61 comprises an internal cylindrical portion 62, an external cylindrical portion 64 and an annular groove 66 formed between the internal cylindrical portion 62 and the external cylindrical portion 64. The outer peripheral surface 63 of the internal cylindrical portion 62 is provided with an engaging part, which is of a reverse tapered shape extending toward the end facing to the sheet metal, for interlocking with the periphery of the bolt insertion hole. The external cylindrical portion 64 has an enlarged end surface abutting to the sheet metal.
However, since these clinch nut 51 and pierce nut 61 have a construction, in which the internal cylindrical portion 52, 62 and the external cylindrical portion 54, 64 are separatedby the annular groove 56, 66, the nut 51, 61 tends to be enlarged in its profile toward the radial direction. As a result, when positioning a plurality of nuts 51, 61 in an adjacent manner, the pitch interval of the respective adjacent nuts 51, 61 becomes lager. Therefore, a problem will arise when fixing a plurality of nuts 51, 61 to a smaller sheet metal such as a small-sized bracket or flange. Meanwhile, if the diameter of the clinch nut 51 and the pierce nut 61 is reduced, the contacting area of the end surface of the external cylindrical portion 54, 64, which abuts to the sheet metal, becomes smaller and hence the joint strength between the nut 51, 61 and the sheet metal is restricted.
With the aforementioned drawbacks of the prior art in view, the present invention seeks to provide a clinch nut assembly, in which a clinch nut can be reduced its size while ensuring a sufficient contacting area with regard to the sheet metal, so that the nut can be firmly fixed to the sheet metal. The present invention also seeks to provide a method for readily producing a clinch nut adapted to use with the clinch nut assembly.
According to a first aspect of the invention, there is provided a clinch nut assembly comprising:
a sheet metal having a bolt insertion hole; and
a clinch nut to be fixed to said sheet metal, wherein said clinch nut is provided with a recess portion at one end facing to the sheet metal so as to receive a tubular projection formed around the bolt insertion hole, and wherein an engaging part is provided around a peripheral wall of said recess portion for interlocking with said tubular projection.
In such a clinch nut assembly, the tubular projection formed around the bolt insertion hole of the sheet metal is fitted into the recess portion provided at one end of the clinch nut, and the tubular projection is forcibly deformed so as to interlock with the engaging part around the peripheral wall of the recess portion. The clinch nut is thereby fixed to the sheet metal with the whole end surface of the clinch nut contacting with the sheet metal.
According to a second aspect of the invention, there is provided a clinch nut assembly comprising:
a sheet metal having a bolt insertion hole;
a clinch nut to be fixed to said sheet metal, the clinch nut including a recess portion at one end facing to the sheet metal so as to receive a tubular projection formed around the bolt insertion hole; and
a washer member fixed to said end of the clinch nut, an inner periphery of the washer member extending inwardly from a peripheral wall of said recess portion so as to form an engaging part for interlocking with said tubular projection.
In such a clinch nut assembly, the tubular projection formed around the bolt insertion hole of the sheet metal is fitted into the recess portion provided at one end of the clinch nut, and the tubular projection is forcibly deformed so as to interlock with the inner periphery of the washer member extending inwardly from the peripheral wall of the recess portion. The clinch nut is thereby fixed to the sheet metal with the whole end surface of the washer member contacting with the sheet metal.
The term xe2x80x9cwasher memberxe2x80x9d in this aspect of the invention indicates a plate-like member having a circular hole, which allows an insertion of the tubular projection of the sheet metal. Usually, the outer profile of the washer member is of circular shape, however, a polygonal shape, such as a square and a hexagon may be employed. The outside dimension of the washer member is decided in accordance with the outside dimension of the clinch nut so that the washer member has substantially the same or slightly greater dimension compared to the clinch nut. The diameter and the thickness of the hole of the washer member are decided in accordance with the thickness of the sheet metal. They may vary as long as retaining a function as an engaging part for interlocking with the tubular projection. The washer member is fixed to the end of the clinch nut by means of resistance welding and the like. For this reason, the washer member is preferably made of the same material as the clinch nut.
According to a third aspect of the invention, the aforementioned clinch nut assemblies further include a flange up washer with a reinforcement tubular projection, and said reinforcement tubular projection pressing an inner peripheral surface of the tubular projection of said sheet metal for interlocking said tubular projection with the clinch nut.
In such a clinch nut assemblies, since the reinforcement tubular projection of the flange up washer presses the inner peripheral surface of the tubular projection of the sheet metal, the clinch nut is more firmly fixed to the sheet metal.
The term xe2x80x9cflange up washerxe2x80x9d in this aspect of the invention indicates a washer, in which a reinforcement tubular projection is formed by way of fluing or flanging up at a center of its flange portion for insertion of a bolt. The reinforcement tubular projection of the flange up washer may be formed together with the tubular projection of the sheet metal with the flange portion attached to the sheet metal. Alternatively, the reinforcement tubular projection may be formed previously and individually. The flange up washer is preferably made of steel with high stiffness so as to firmly retain the interlocking state with regard to the tubular projection of the sheet metal. The flange portion of the flange up washer is not limited to a circular shape and may be polygonal, such as square and hexagonal. However, it is usually formed as a circular shape with substantially the same outside dimension of the clinch nut.
According to a fourth aspect of the invention, the clinch nut assembly according to the first aspect of the invention is characterized in that the sheet metal has a plurality of adjacent bolt insertion holes, and that a flange up washer plate with a plurality of reinforcement tubular projections is attached to the sheet metal in such a way that each of said plurality of reinforcement tubular projections presses an inner peripheral surface of the corresponding tubular projection for interlocking the tubular projection with the clinch nut.
In such a clinch nut assembly, since the flange up washer plate is attached to the sheet metal in such a way that each of the plurality of reinforcement tubular projections presses the inner peripheral surface of the corresponding tubular projection, a plurality of clinch nuts are adjacent to each other and they are more firmly fixed to the sheet metal.
The term xe2x80x9cflange up washer platexe2x80x9d indicates a plate member having a plurality of reinforcement tubular projections, such as the reinforcement tubular projection of the flange up washer according to the third aspect of the invention. Similar to the reinforcement tubular projection of the flange up washer, the plurality of reinforcement tubular projections of the flange up washer plate are formed by way of fluing. Also, similar to the flange up washer, the flange up washer plate is preferably made of steel with high stiffness.
In the clinch nut assembly in which the flange up washer or the flange up washer plate is attached to the clinch nut, a front end of the reinforcement tubular projection may be bent outwardly so as to encompass the tubular projection of the sheet metal. In such a clinch nut assembly, since the front end of the reinforcement tubular projection provided on the flange up washer or the flange up washer plate as well as the tubular projection of the sheet metal is engaged with the peripheral wall of the recess portion of the clinch nut, the clinch nut is more firmly fixed to the sheet metal.
According to a fifth aspect of the invention, there is provided a clinch nut assembly comprising:
a sheet metal having a bolt insertion hole;
a clinch nut to be fixed to said sheet metal; and
a flange up washer with a reinforcement tubular projection, wherein said clinch nut includes a recess portion at one end facing to the sheet metal so as to receive said reinforcement tubular projection which is inserted through the bolt insertion hole of said sheet metal, and wherein an engaging part is provided around a peripheral wall of said recess portion for interlocking with the reinforcement tubular projection of said flange up washer in such a way that the sheet metal is retained between said one end of the clinch nut and a flange portion of said flange up washer.
In such a clinch nut assembly, the reinforcement tubular projection of the flange up washer is inserted through the bolt insertion hole of the sheet metal and is fitted into the recess portion formed at one end of the clinch nut, and then the reinforcement tubular projection is forcibly deformed so as to interlock with the engaging part provided around the peripheral wall of the recess portion. Therefore, the clinch nut is fixed to the sheet metal with the sheet metal retained between the end surface around the recess portion and the flange portion of the flange up washer.
The reinforcement tubular projection of the flange up washer according to the fifth aspect of the invention may be formed previously by way of fluing. Alternatively, the reinforcement tubular projection may be formed by way of fluing upon deforming the flange up washer with regard to the peripheral wall of the recess portion of the clinch nut.
According to a sixth aspect of the invention, there is provided a method of producing a clinch nut according to the first aspect of the invention, comprising the steps of:
forming a bead-like excess metal portion on a semi-finished molding product at one end having a recess portion and at the innermost periphery adjacent to the recess portion; and
stamping the excess metal portion so as to form an engaging part around the peripheral wall of the recess portion.
In such a method, since the bead-like excess metal portion to be stamped is provided on one end of the semi-finished molding product at the innermost periphery adjacent to the recess portion, when the bead-like excess metal portion is stamped, the engaging part, which projects from the peripheral wall of the recess portion, is formed by the plastic deformation. Therefore, the clinch nut is readily manufactured.